The thing about blue collar work is you have to truely enjoy it. That is what you ae going to be doing all the time. You are going to sweat in the summer and freeze in the winter. You are going to get cuts and scratches, you are going to get banged up. You are going to get dirty. It's hard work. If you don't truely like hard work, you are going to be miserable. It's almost a passion, you can't explain it, thats just the way it is.
As for me, I knew what I wanted to do with my life when I was 10. At 13(freshman year), I started tech school. Now, I know that everyone says that tech school is for losers that don't want to go to real high school. That is true in many cases, I went to school with a lot of morons. If you are there to learn, though, it can be an invaluable tool for the future. So, i went there, got a job in the field when I graduated, and have been doing it ever since. I've never set foot in a college. I'm now 27 and make around 60g a year. It's not crazy money, but I ENJOY going to work and it is enough to be comfortable. Think about it. I see my coworkers more than I see my wife. It is important that you enjoy your job. If someone were to offer me twice the money to work at a desk, I would walk away laughing. It's just not me. Some people get too caught up in the money and end up leading unhappy lives. Also, in these hard economical times, I know that with the skills I have, I am going to stay employed. I have friends that put in 4 years of college and now work part time at starbucks. I still have people asking me to quit my job and come work for them. Maybe I am an exception to the rule, I don't know.
You are right, you need to make these decisions now. If you pick the blue collar route, what are you interested in? I mean, anyone can grab a shovel and go to work. What do you like to do? If you go the white collar route, will you be happy? Or are you going to be watching the clock, counting the minutes, for the rest of your life? If you wait much longer, you will find yourself 35 and working at moobys.
Basicly, what I am getting at is do what you like. If you like a climate controlled environment and a comfy office chair, then get a desk job. If you like using your hands, then grab a shovel.